NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC 275 



these stations there should consequently, as a rule, be a negative 

 correlation, as Dr. Clayton has found. 



Roswell, in New Mexico, has a more northerly position than San 

 Diego, in 33° 24' N., 104^ 27' W., far outside the tropical regions, 

 but has nevertheless a positive correlation, though not much de- 

 veloped. 



According to Buchan's charts [1889], the prevailing winds in this 

 region during the months of July to October should be southerly 

 or southeasterly, dependent on the Atlantic pressure maximum. A 

 raising .of this maximum, by increased solar activity, might there- 

 fore be expected to raise the temperature at Roswell. But the 

 positive correlation thus produced cannot be expected to be well 

 developed, as the station is situated between the two centers of 

 action (the pressure maxima) of the North Pacific and the North 

 Atlantic. A shift in these centers of action may easily reverse the 

 winds at Roswell. 



At Mauritius, situated in 20° 6' S. inside the tropical region, the 

 prevailing winds are southeasterly. An increased activity of the 

 winds by an increased solar activity, ought therefore to lower the 

 temperature ; and we may expect to find a well developed negative 

 correlation at this station, which is also the case. 



San Isidro, Manila, in the Philippines, is situated in 15° 22' N., 

 120° 53' E. The prevailing winds during the months of July to 

 September are southwesterly, during November, northeasterly, and 

 during October, variable, according to Alexander Buchan's maps. 

 Dr. Clayton finds a well-developed positive correlation for this sta- 

 tion. But at Hongkong, situated on the continent at a comparatively 

 short distance to the northwest (in 22° 18' N., 114° 10' E., the 

 conditions are diflferent. The prevailing winds during July and 

 August are southeasterly, during September-October-November 

 northeasterly. An increase of both these kinds of winds, by in- 

 creased solar activity, may be expected to lower the temperature at 

 Hongkong. The southeasterly winds are sea-winds which during 

 the hot season bring colder air in over the continent, while the 

 temperature will rise when there is no wind or light land breezes. 

 The sea-winds are also moist and will consequently bring more 

 cloudiness, which will lower the daily maximum temperatures with 

 which Dr. Clayton operates. We should therefore expect to find 

 a negative correlation at Hongkong during the months of July to 

 November, which is also the case. 



